Hi, I'm using a L293D H-bridge to control two 3v motors, and controlling this with arduino. To power the motors I'm using a Lm7805 5v voltage regulator to power the motors (them work good in 5v). The problem is that when I use the h-bridge with an external power, it works really good, but when I power it with the same 9v battery used to control the arduino (while this is powering the arduino), they don't work (of course, regulating the voltage with Lm7805). I can see that them try to move, but they can't.